3.4. Link Establishment Phase

3.4. Link Establishment Phase

The Link Control Protocol (LCP) is used to establish the connection
through an exchange of Configure packets. This exchange is complete,
and the LCP Opened state entered, once a Configure-Ack packet
(described later) has been both sent and received.

All Configuration Options are assumed to be at default values unless
altered by the configuration exchange. See the chapter on LCP
Configuration Options for further discussion.

It is important to note that only Configuration Options which are
independent of particular network-layer protocols are configured by
LCP. Configuration of individual network-layer protocols is handled
by separate Network Control Protocols (NCPs) during the Network-Layer
Protocol phase.

Any non-LCP packets received during this phase MUST be silently
discarded.

The receipt of the LCP Configure-Request causes a return to the Link
Establishment phase from the Network-Layer Protocol phase or
Authentication phase.